Sony UP-21MD Service Manual page 69

9. inieriock sensor
Type: Mechanical type
Function: Detects whether bottom plate is installed on the unit. When bottom plate is not installed on
the unit, turn off the power of the unit.
Level: MEC-15 board CN201 7P
H: Power ON
L: Power OFF
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CN201
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4-3-5. Head Control Biock
The head control block corrects the parallel print data per line from the VPR-74 board and transfers it to
the thermal head for printing.
The head control block consists of the following five blocks.
* Color table y RAM plus temperature correction offset (IC501) that y-corrects the parallel print data
from VPR-74 board
* Image processing circuit (picture quality control) (IC502) that performs pattern recognition
interpolation, edge emphasis, and thermal storage correction
* Head drive circuit (IC401, 403) that PWM-converts parallel data and transfers print data to the thermal
head
* Line number correction circuit (voltage drop control) (IC402) that corrects the voltage drop due to the
common resistor of a thermal head
* Head voltage correction circuit
Print data is received from the VPR-74 board as parallel data, 'y-corrected, and processed by a PQC
circuit. After that, the print data is PWM-modulated using a head drive circuit and transferred to the
thermal head via CN401 on the SY-299 board.
y correction circuit
The print data sent from the VPR-74 board is y-corrected using the data conversion table of yRAM
(IC501). Before printing, the y data of each YMC color corresponding to the media type, paper feeding
and ¥ type is written in the address of YRAM. ICS01 also accounts two data offset for temperature
correction of continuity printing and color balance functions, and then add it to print data.
UP-21MD V1 4-31